Orthodontic treatment of improperly positioned teeth involves the application of mechanical forces to urge the teeth into correct alignment and orientation. The most common form of treatment involves use of orthodontic brackets which are small slotted bodies configured for direct attachment to the front or labial surfaces of the teeth, or alternatively for attachment to bands which are in turn cemented or otherwise secured around the teeth. A resilient curved arch wire is then seated in the bracket slots, and the arch wire is bent or twisted before installation whereby the restoring force exerted by the seated resilient wire tends to shift the teeth into orthodontically correct alignment. Depending on the shape of the arch wire (both round and rectangular cross-sections are in common use) and the orientation of the bracket slot, it is possible to apply forces which will shift, rotate or tip the teeth in any desired direction.
Conventional orthodontic brackets include tie wings around which small ligature wires are tied to hold the arch wire in a securely seated position in the brackets. Ligatures or some other form of fastening means are essential to insure that the activated arch wire is properly positioned around the dental arch, and to prevent the wire from being dislodged from the bracket slots during chewing of food, brushing of the teeth, or application of other forces to the wire by the patient.
Orthodontists develop great skill in the manipulation of ligatures, but the installation of these small wires nevertheless requires considerable time during initial installation of an arch wire. It is also normally necessary to remove and replace the ligatures at one or more intermediate stage of orthodontic treatment involving sequential use of several different kinds of arch wires, leading to further essentially unproductive chair time for the orthodontist and possible discomfort for the patient. Ligatures also tend to make proper oral hygiene more difficult as the wires can trap food particles, and the twisted ends of a ligature may be shifted during chewing into a position where irritation of the patient's gums or cheek tissue occurs. Broken or dislodged ligatures may also require emergency patient visits to the orthodontist, and broken ligatures further present the hazard that a loose piece of wire may be swallowed or inhaled into the patient's breathing passages.
The bracket assembly of this invention eliminates the need for ligatures at most or all stages of treatment. A rotatable locking member is captively mounted in a bracket body, and is movable between open and closed positions to receive and lock an arch wire in a seated position. Simple rotation of the locking member enables rapid initial installation of an arch wire, and significantly facilitates exchange of arch wires during intermediate treatment phases. The locking member is easily manipulated by auxiliary personnel to minimize the time required for the orthodontist to insure proper installation or exchange of arch wires.
The bracket is smoothly contoured to minimize food-trapping recesses, and includes extensions or steps at each end of the arch-wire slot for improved application of force to teeth requiring rotation. The locking member is useful in both light-wire and edgewise techniques without restriction on arch-wire cross-section, and does not restrict orientation of the arch-wire slot to enable application of torquing or other force vectors. Tie wings may be provided on the bracket to enable ligation of an arch wire which cannot be fully seated in the bracket during early treatment of a severely malpositioned tooth or in any case where complete bracket engagement is difficult or unattainable.